<?php
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2016, British Columbia Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package    CodeIgniter
 * @author    EllisLab Dev Team
 * @copyright    Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
 * @copyright    Copyright (c) 2014 - 2016, British Columbia Institute of Technology (http://bcit.ca/)
 * @license    http://opensource.org/licenses/MIT	MIT License
 * @link    https://codeigniter.com
 * @since    Version 3.0.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * PHP ext/hash compatibility package
 *
 * @package        CodeIgniter
 * @subpackage    CodeIgniter
 * @category    Compatibility
 * @author        Andrey Andreev
 * @link        https://codeigniter.com/user_guide/
 * @link        http://php.net/hash
 */

// ------------------------------------------------------------------------

if (is_php('5.6')) {
    return;
}

// ------------------------------------------------------------------------

if (!function_exists('hash_equals')) {
    /**
     * hash_equals()
     *
     * @link    http://php.net/hash_equals
     * @param    string $known_string
     * @param    string $user_string
     * @return    bool
     */
    function hash_equals($known_string, $user_string)
    {
        if (!is_string($known_string)) {
            trigger_error('hash_equals(): Expected known_string to be a string, ' . strtolower(gettype($known_string)) . ' given', E_USER_WARNING);
            return FALSE;
        } elseif (!is_string($user_string)) {
            trigger_error('hash_equals(): Expected user_string to be a string, ' . strtolower(gettype($user_string)) . ' given', E_USER_WARNING);
            return FALSE;
        } elseif (($length = strlen($known_string)) !== strlen($user_string)) {
            return FALSE;
        }

        $diff = 0;
        for ($i = 0; $i < $length; $i++) {
            $diff |= ord($known_string[$i]) ^ ord($user_string[$i]);
        }

        return ($diff === 0);
    }
}

// ------------------------------------------------------------------------

if (is_php('5.5')) {
    return;
}

// ------------------------------------------------------------------------

if (!function_exists('hash_pbkdf2')) {
    /**
     * hash_pbkdf2()
     *
     * @link    http://php.net/hash_pbkdf2
     * @param    string $algo
     * @param    string $password
     * @param    string $salt
     * @param    int $iterations
     * @param    int $length
     * @param    bool $raw_output
     * @return    string
     */
    function hash_pbkdf2($algo, $password, $salt, $iterations, $length = 0, $raw_output = FALSE)
    {
        if (!in_array(strtolower($algo), hash_algos(), TRUE)) {
            trigger_error('hash_pbkdf2(): Unknown hashing algorithm: ' . $algo, E_USER_WARNING);
            return FALSE;
        }

        if (($type = gettype($iterations)) !== 'integer') {
            if ($type === 'object' && method_exists($iterations, '__toString')) {
                $iterations = (string)$iterations;
            }

            if (is_string($iterations) && is_numeric($iterations)) {
                $iterations = (int)$iterations;
            } else {
                trigger_error('hash_pbkdf2() expects parameter 4 to be long, ' . $type . ' given', E_USER_WARNING);
                return NULL;
            }
        }

        if ($iterations < 1) {
            trigger_error('hash_pbkdf2(): Iterations must be a positive integer: ' . $iterations, E_USER_WARNING);
            return FALSE;
        }

        if (($type = gettype($length)) !== 'integer') {
            if ($type === 'object' && method_exists($length, '__toString')) {
                $length = (string)$length;
            }

            if (is_string($length) && is_numeric($length)) {
                $length = (int)$length;
            } else {
                trigger_error('hash_pbkdf2() expects parameter 5 to be long, ' . $type . ' given', E_USER_WARNING);
                return NULL;
            }
        }

        if ($length < 0) {
            trigger_error('hash_pbkdf2(): Length must be greater than or equal to 0: ' . $length, E_USER_WARNING);
            return FALSE;
        }

        $hash_length = strlen(hash($algo, NULL, TRUE));
        empty($length) && $length = $hash_length;

        // Pre-hash password inputs longer than the algorithm's block size
        // (i.e. prepare HMAC key) to mitigate potential DoS attacks.
        static $block_sizes;
        empty($block_sizes) && $block_sizes = array(
            'gost' => 32,
            'haval128,3' => 128,
            'haval160,3' => 128,
            'haval192,3' => 128,
            'haval224,3' => 128,
            'haval256,3' => 128,
            'haval128,4' => 128,
            'haval160,4' => 128,
            'haval192,4' => 128,
            'haval224,4' => 128,
            'haval256,4' => 128,
            'haval128,5' => 128,
            'haval160,5' => 128,
            'haval192,5' => 128,
            'haval224,5' => 128,
            'haval256,5' => 128,
            'md2' => 16,
            'md4' => 64,
            'md5' => 64,
            'ripemd128' => 64,
            'ripemd160' => 64,
            'ripemd256' => 64,
            'ripemd320' => 64,
            'salsa10' => 64,
            'salsa20' => 64,
            'sha1' => 64,
            'sha224' => 64,
            'sha256' => 64,
            'sha384' => 128,
            'sha512' => 128,
            'snefru' => 32,
            'snefru256' => 32,
            'tiger128,3' => 64,
            'tiger160,3' => 64,
            'tiger192,3' => 64,
            'tiger128,4' => 64,
            'tiger160,4' => 64,
            'tiger192,4' => 64,
            'whirlpool' => 64
        );

        if (isset($block_sizes[$algo]) && strlen($password) > $block_sizes[$algo]) {
            $password = hash($algo, $password, TRUE);
        }

        $hash = '';
        // Note: Blocks are NOT 0-indexed
        for ($bc = ceil($length / $hash_length), $bi = 1; $bi <= $bc; $bi++) {
            $key = $derived_key = hash_hmac($algo, $salt . pack('N', $bi), $password, TRUE);
            for ($i = 1; $i < $iterations; $i++) {
                $derived_key ^= $key = hash_hmac($algo, $key, $password, TRUE);
            }

            $hash .= $derived_key;
        }

        // This is not RFC-compatible, but we're aiming for natural PHP compatibility
        return substr($raw_output ? $hash : bin2hex($hash), 0, $length);
    }
}
